A field experiment was carried out in 2009–2010 on the area of the Didactic and Experimental Farm in Swadzim, University of Life Sciences in Poznań. The aim of the experiment was to study the effect of different nitrogen doses on the infection level of two types of maize cultivars infected by the following disease casual agents: Fusarium spp. and Ustilago maydis. Both, the intensity of occurrence of fusariosis and corn smut was determined. The studied levels of nitrogen doses significantly affected the degree of disease infection of maize. Maize hybrid „stay-green” type was significantly less infected by the pathogens Fusarium spp. and U. maydis.